Most amplifiers have push-pull output devices that are biased in a Class-AB manner. Such amplifiers draw a nominal quiescent current from the power supplies that must be at a voltage high enough to drive the largest output signal, even if the majority of the output signal is relatively low, with only occasional large peaks. For example, in the case of Digital Subscriber Line (DSL) signals, the majority of the signal is at a relative low level, with only occasional large output peaks. This results in the standard Class-AB output stage wasting about five times the delivered output power. Accordingly, Class-AB amplifiers are inefficient in that they waste a large amount of power. It is desirable to provide more efficient amplifiers.